Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!intran!tom
From: tom@intran.UUCP (Tom B.)
Newsgroups: comp.robotics
Subject: Re: Looking for information about cheap gyroscope
Summary: Compass, and Gyroscpes should be used together
Keywords: gyroscope, navigation, orientation
Message-ID: <361@intran.UUCP>
Date: 12 Jun 91 18:33:47 GMT
References: <00--VV-@engin.umich.edu>
Organization: Xerox/Intran Corp, Mpls
Lines: 28


I have some experience with Magnetic Flux Gate compasses (about a year ago 
Radio Electronics published how to modify the Car Compass for computers).  
and I currently have the Dinsmore Device (4 hall effect transistors) in an
underwater robot.  Also a student pilot.

The Compass and gyro should both be used together on land based robots.

Reasons:

a. Compass is affected by metalic objects in buildings, ground, etc.

b. Gyro's have a tendency to precess (drift) due to friction, and other
    mechanical factors.

c. Compass can be used to "normalize" gyro inputs.  


While flying an airplane, a pilot much reset the gyro to the magnetic compass
every 10-15 minutes.  the Gyro is used for flying, but the compass is accurate.
The airplane must be in straight and level flight to use the magnetic compass
because in turns the compass will hang, lead, or follow the actual direction.
The gyro may also lead in a turn, or indicate opposite direction at the start of
a turn, but this maybe due to adverse yaw.

I hope this information is useful

Tom Brusehaver